1. Field of the Invention
This invention relates to a thermosensitive recording material having excellent keeping quality of developed color images.
2. Description of the Prior Art
Generally, thermosensitive recording material is made by forming on a support a thermosensitive recording layer composed principally of a usually colorless or light-color electron donative dye precursor and an electron receptive color developer. When the recording material is heated by a heating means such as thermal head, thermal pen, laser light, etc., the dye precursor and color developer are reacted instantaneously and a color image is recorded. The relating art is disclosed in Japanese Patent Publication Nos. 4160/68 and 14039/70 and other literatures. Such thermosensitive recording material has the specific advantages such that recording can be made with a relatively simple apparatus, maintenance of the material is easy, no noise is generated in the recording operation, etc., and thanks to these features, it is now utilized in a wide range of recording systems and devices such as, for instance, measurement recorders, facsimiles, printers, computer terminals, labelers, and ticket vending machines.
It is the basic requirements for a thermosensitive recording material that it has a sufficient color image density and sensitivity and that it causes no quality deterioration of the developed color image with time. Also, with expansion of the scope of use of thermosensitive recording material in recent years, it has become the vital requirements that the obtained image suffers no deleterious change by the adhesion of oily matter such as hair cream, hand cream, oils and fats contained in skin perspiration, etc. (oil resistance of the image), or by the adhesion of water (water resistance of the image).